This build is under development, since I am still experimenting with Orianna, but here are the infos I gattered so far about her =)

My personal impressions
She is a ton of fun, especially once you can just throw your balls around continuously. The ball is not *too* hard to understand but it can take a while to adapt to it during a stressful situation. The fact that you cant activate your skills in advance while the ball is moving is frustrating though and defenitly slows you down, I hope Riot planned to fix it. Quite annoying to have to continuously press W to make sure it activates as soon as the ball stops.

Feel free to leave your comments but keep in mind that this build is far from finished and that I'm only publishing it to show my observations on her. Obviously, I am no expert of Orianna since she came out only a few days ago so everything in this build are theories and obvservations.

Pros
Good range
Good farmer
Can check bushes with her balls
Awesome crowd control
Fun once you get used to her
Get to say balls jokes for the entire game

Cons
Very squishy
Has a slow start
Mind puzzling at first

What I get
or You absolutly need an escape mechanism since you will be very squishy and probably targeted for most of the game
Can be used both Offensively and Defensively, I defenitly recommand this as a second choice

What not to get
Her abilities are very cheap once you start getting your mana
You are not a jungler
No need to explain

Classic 9/0/21

Skill Sequence
-I always keep my 1 level above everything else since it is your main skill
-Leveling both and allows you to increase both your defense and offense, considering how squishy you are, the extra shield is very welcome.

Starter

Like most mages, you will be very low on mana early game so you need all you can get. Health potions are always good as well since you will only start with 400 hp.

Ideal first trip back to base

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You want to get extra movement speed since you are very squishy and can get taken down easily if you're too slow

You already starts buiding your cooldown which will allow you to do more damage more quickly

Like i've heard around, Orianna's true potential starts at mid-game where she starts getting more ability power and is able to do lots of burst. She is very squishy so you have to be careful until you get your core.

Early game, her mana gets depleted very quickly, I would recommand to restrict your use of dissonance and just harass with the command which costs less mana.

Mid game, you can start harassing more and lower your enemies enough so that you can finish them with your ATT/SHOCK/DISS/SHIELD + autoattack